1. Field of the Invention
The present invention is-drawn generally to the field of human-machine systems, wherein control of the system by a human operator is enhanced by adapting the control functions of the system to accommodate or identify changes in operator performance. More specifically, the present invention provides for measurement or application of disturbances in the control system which elicit operator response. Characterization of the response is then employed to adapt the control functions of the system for sensitivity or mode consistent with operator needs.
2. Prior Art
The present approach to "man in the loop" control of systems relies on observance of the control inputs of a human operator to either obtain a direct control response, or to provide control through a transfer function, which is characterized by previously modeled human control behavior. The second approach is obviously desirable where significant changes may occur in the control requirements for operation of the system. For example, a power steering system of an automobile may require different sensitivities depending on the speed of the automobile. Sensitive steering at slow speeds to allow maneuvering into parking spaces and other precise maneuvering requirements is desirable. However, at highway speeds on straight stretches of highway, high sensitivity could create over control or require greater operator attention than is necessary.
Various means may be employed to obtain controlled ranges or functions in the machine system based on human input. As an example, switches, knobs and other interface devices may be employed to allow the operator to directly control adaptation of the system. Automobile manual transmissions are an example of this type of adaptation. The operator directly selects the gear of the transmission to allow a specific range of operating responses from the automobile. The second type of control system may be an automated response to an unambiguous signal from the operator. The typical mechanism in automobiles which activates anti-lock braking systems for rapid stopping is initiated by a specific pressure level placed by the operator on the brake pedal consistent with a "hard stop." A second example of this type is "floor-boarding" of the accelerator to contact a microswitch to create a downshifting of an older style automatic transmission into passing gear. The third type of adaptation relies on preprogrammed sequences which monitor direct parametric results of control by the operator. An example of this type of system is an automobile automatic transmission, wherein the transmission determines the appropriate gear based on engine RPM or speed and transmission load, which is indirectly established by the operation of the accelerator pedal by the driver.
Each of these three prior art methods is appropriate under certain circumstances; however, each contains serious drawbacks. The first two methods are not autonomous and therefore are limited by attention, resources, speed, and accuracy of the human operator and can consume additional attention resources of the operator by requiring direct cognition and action. Further, the adaptation of the system is limited to a range that can be learned and performed by a human operator.
Preprogrammed sequences of adaptations do not react to changes in behavior of the human operator, relying only on a preprogrammed response to other system parameters. Certain prior art systems have attempted to model human behavior to obtain heuristic solutions to specific problems. Creating a gear change in an automatic transmission when the accelerator pedal is floor boarded by an operator is a simple example of this approach. Action by the operator to pass a vehicle results in depressing the accelerator pedal to increase speed. If additional speed is necessary, the operator presses the accelerator pedal more firmly, ultimately depressing the pedal fully to the floor thereby achieving the downshift in the transmission to a passing gear. This sequence is a natural control pattern for the operator. Similarly, tailoring of power steering systems for sensitivity based on speed employs modeling of human reactions to slow speed and high speed road conditions to create the control transfer function employed by the power steering unit at various speeds and then applying the model based only on speed of the vehicle.
Creating a truly adaptable control for a human-machine system requires knowledge of the process of human control rather than merely the result. The prior systems monitor what the operator is doing, but not how the operator is accomplishing the control. While prior art modeling techniques may employ disturbance inputs to detect operator reaction for modeling purposes, directly employing the reaction of the human operator to such disturbance in an adaptive control system has not been accomplished. It is therefore desirable to create a method and apparatus for human-machine system adaptive control which is autonomous thereby not requiring the attention of the operator, allowing use in the system when the operator is too busy to perform manual adaptation well or at all, and to provide rapid and effect adaptation over a broad range of responses.